This invention relates to a pull type master cylinder and more particularly to an improved fabricated master cylinder and a valving arrangement therefor.
Fluid cylinders are employed for a wide variety of purposes. For example, in automotive applications a fluid cylinder may be employed as the actuating device for the vehicular brakes or clutch. Such fluid cylinders normally include the fluid motor per se and a reservoir for containing fluid for makeup to the cylinder to compensate for wear in the system or fluid losses. Frequently, these master cylinders are formed as castings. Although the use of castings for this purpose has a number of advantages, such as low cost, there are also disadvantages to such one piece cast constructions.
In the first instance, when a master cylinder and reservoir are formed as an integral component, it is necessary that all parts of the master cylinder housing be formed from the same material. This, of course, limits the choice of materials and frequently results in a heavier than desired construction. In addition, the use of cast master cylinders gives rise to certain other disadvantages, particularly where machining operations are required internally of the cylinder housing.
For example, in a type of master cylinder known as a "pull type" the piston is actuated by applying a pulling force rather than a pushing force to it. With this type of system, it is the practice to provide a recuperation valve that extends through the piston so as to permit makeup fluid to flow through the piston to the pressurized side on release or return operation to pass makeup fluid if required. These valves normally employ a position responsive member so that the valve will be manually opened when the piston is moved to its at rest position. As a result, it is necessary to provide some form of stop or shoulder for operating the valve and this frequently necessitates the machining of a shoulder or of a retainer portion to hold a stop in the bore. As a result, the cost savings of the cast construction may be lost.
It is, therefore, a principal object of this invention to provide an improved, simplified and fabricated master cylinder assembly.
It is a further object of this invention to provide a fabricated master cylinder assembly wherein machining operations can be substantially reduced.
It is another object of the invention to provide a fabricated master cylinder assembly that permits the use of different types of materials for the components of the master cylinder.